1. Field of the Invention
Embodiments of invention relate generally to optical devices and, more specifically but not exclusively relate to amplifying and/or attenuating optical power in optical beams.
2. Background Information
The need for fast and efficient optical-based technologies is increasing as Internet data traffic growth rate is overtaking voice traffic pushing the need for fiber optical communications. Transmission of multiple optical channels over the same fiber in the dense wavelength-division multiplexing (DWDM) system provides a simple way to use the unprecedented capacity (signal bandwidth) offered by fiber optics. Commonly used optical components in the system include wavelength division multiplexed (WDM) transmitters and receivers, optical filter such as diffraction gratings, thin-film filters, fiber Bragg gratings, arrayed-waveguide gratings, optical add/drop multiplexers, optical amplifiers and optical attenuators.
An optical amplifier is a device that can be used to increase the optical intensity or power of an optical beam while an optical power attenuator is a device that can be used to limit the intensity of light transmitted by the device to some value. An optical amplifier can be useful to for example increase the intensity of an optical beam to compensate for power loss before or after being transmitted from a source to a destination. Optical power attenuators can be useful for a number of purposes including protecting human eyes, photodetectors or the like from high intensity light. Known optical power attenuators include solid-state optical power attenuators based on photoconductivity and the electro-optic effect has been observed in electro-optic crystals. Other known materials used for optical power limiting include molecular materials such as matallophthalocyanines and metallonaphthalocyanines, which exhibit relatively low linear absorption and high ratios of exited-state to ground-state absorption. Christiansen filters have also been utilized in optical power attenuator applications to limit the maximum power transmitted by a device to some fixed value. Christiansen filters include for example small grains of crushed glass mixed with a liquid exhibiting a precise linear refractive index such that the glass grains disappear into the host liquid. An index mismatch between the liquid and glass components is induced by exposure to high intensity light, which therefore results in the optical power attenuator behavior in the device. Use of the known optical power attenuators such as those summarized above has been limited due to their complexity and the challenges involved with integrating and combining these technologies with other optical technologies into practical solutions.